From: Jianbo Liu <jianbo.liu@arm.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>
Cc: Yongseok Koh <yskoh@mellanox.com>,
adrien.mazarguil@6wind.com, nelio.laranjeiro@6wind.com,
jerin.jacob@caviumnetworks.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2 1/8] eal: introduce DMA memory barriers
Date: Tue, 16 Jan 2018 17:10:41 +0800 [thread overview]
Message-ID: <20180116091040.GA15629@arm.com> (raw)
In-Reply-To: <af050403-2404-1364-bfa7-d65ab312180c@solarflare.com>
The 01/16/2018 10:49, Andrew Rybchenko wrote:
> On 01/16/2018 04:10 AM, Yongseok Koh wrote:
> >This commit introduces rte_dma_wmb() and rte_dma_rmb(), in order to
> >guarantee the ordering of coherent shared memory between the CPU and a DMA
> >capable device.
> >
> >Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> >---
> > lib/librte_eal/common/include/generic/rte_atomic.h | 18 ++++++++++++++++++
> > 1 file changed, 18 insertions(+)
> >
> >diff --git a/lib/librte_eal/common/include/generic/rte_atomic.h b/lib/librte_eal/common/include/generic/rte_atomic.h
> >index 16af5ca57..2e0503ce6 100644
> >--- a/lib/librte_eal/common/include/generic/rte_atomic.h
> >+++ b/lib/librte_eal/common/include/generic/rte_atomic.h
> >@@ -98,6 +98,24 @@ static inline void rte_io_wmb(void);
> > */
> > static inline void rte_io_rmb(void);
> >+/**
> >+ * Write memory barrier for coherent memory between lcore and IO device
> >+ *
> >+ * Guarantees that the STORE operations on coherent memory that
> >+ * precede the rte_dma_wmb() call are visible to I/O device before the
> >+ * STORE operations that follow it.
> >+ */
> >+static inline void rte_dma_wmb(void);
> >+
> >+/**
> >+ * Read memory barrier for coherent memory between lcore and IO device
> >+ *
> >+ * Guarantees that the LOAD operations on coherent memory updated by
> >+ * IO device that precede the rte_dma_rmb() call are visible to CPU
> >+ * before the LOAD operations that follow it.
> >+ */
> >+static inline void rte_dma_rmb(void);
> >+
> > #endif /* __DOXYGEN__ */
> > /**
>
> I'm not an ARMv8 expert so, my comments could be a bit ignorant.
> I'd like to understand the difference between io and added here dma
> barriers.
> The difference should be clearly explained. Otherwise we'll constantly hit
> on incorrect choice of barrier type.
> Also I don't understand why "dma" name is chosen taking into account
> that definition is bound to coherent memory between lcore and IO device.
A good explanation can be found here.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1077fa36f23e259858caf6f269a47393a5aff523
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next prev parent reply other threads:[~2018-01-16 9:12 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-27 4:28 [dpdk-dev] [PATCH 1/2] eal/arm64: modify I/O device " Yongseok Koh
2017-12-27 4:28 ` [dpdk-dev] [PATCH 2/2] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-04 12:58 ` [dpdk-dev] [PATCH 1/2] eal/arm64: modify I/O device memory barriers Jerin Jacob
2018-01-08 1:55 ` Jianbo Liu
2018-01-16 0:42 ` Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 0/8] introduce DMA " Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 1/8] eal: " Yongseok Koh
2018-01-16 2:47 ` Jianbo Liu
2018-01-16 7:49 ` Andrew Rybchenko
2018-01-16 9:10 ` Jianbo Liu [this message]
2018-01-17 13:46 ` Thomas Monjalon
2018-01-17 18:39 ` Yongseok Koh
2018-01-18 11:56 ` Andrew Rybchenko
2018-01-18 18:14 ` Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 2/8] eal/x86: define " Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 3/8] eal/ppc64: define DMA device " Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 4/8] eal/armv7: define DMA " Yongseok Koh
2018-01-16 2:48 ` Jianbo Liu
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 5/8] eal/arm64: " Yongseok Koh
2018-01-16 2:50 ` Jianbo Liu
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 6/8] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 7/8] net/mlx5: replace IO memory barrier with DMA " Yongseok Koh
2018-01-16 1:10 ` [dpdk-dev] [PATCH v2 8/8] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-16 3:53 ` Jianbo Liu
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 0/8] introduce DMA memory barriers Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 1/8] eal: " Yongseok Koh
2018-01-19 7:16 ` Andrew Rybchenko
2018-01-22 18:29 ` Yongseok Koh
2018-01-22 20:59 ` Thomas Monjalon
2018-01-23 4:35 ` Jerin Jacob
2018-01-25 19:08 ` Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 2/8] eal/x86: define " Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 3/8] eal/ppc64: " Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 4/8] eal/armv7: " Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 5/8] eal/arm64: " Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 6/8] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 7/8] net/mlx5: replace IO memory barrier with DMA " Yongseok Koh
2018-01-19 0:44 ` [dpdk-dev] [PATCH v3 8/8] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 0/9] introduce coherent I/O memory barriers Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 1/9] eal: add Doxygen grouping for " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 2/9] eal: introduce coherent I/O " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 3/9] eal/x86: define " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 4/9] eal/ppc64: " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 5/9] eal/armv7: " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 6/9] eal/arm64: " Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 7/9] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 8/9] net/mlx5: replace I/O memory barrier with coherent version Yongseok Koh
2018-01-25 21:02 ` [dpdk-dev] [PATCH v4 9/9] net/mlx5: fix synchronization on polling Rx completions Yongseok Koh
2018-01-28 7:32 ` [dpdk-dev] [PATCH v4 0/9] introduce coherent I/O memory barriers Thomas Monjalon
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